Just to comment,
I know EXACTLY what you're talking about.
I've had this feeling before as well. For me, it seems to come most often when I'm in a very "spiritual" state, or when I'm having a deep conversation about a spiritual matter. It normally happens in the afternoon/evening.
There were actually a couple of times when I drifted up out of my body and looked down. My body was still in a deep discussion about a spiritual matter! It just kept on talking!
Very strange, no?
So yea, I just felt the urge to comment and say, you are not alone. And, on a side note, you may want to just allow or expect anything to happen when you have this feeling. Just a thought.